In an open monocentric phase II study, 20 inpatients with hypertension were treated with a single daily dose of nilvadipine for 3 weeks after a 1-week placebo washout phase. The initial dose in all patients was 8 mg/day p.o.; this was doubled to 16 mg once daily if an adequate blood pressure reduction was not achieved after 10 days on 8 mg. The objective of the study was to investigate the effect of this new calcium antagonist on the blood pressure in hypertensive patients. This was done by means of a 24-h blood pressure profile (with measurements at 0.5, 1, 2, 4, 8, 12, and 24 h after administration), and over the complete course of the treatment period (blood pressure measurements each day just before the medication was given). In addition, by determination of the nilvadipine plasma levels on the first, tenth, and last medication day, a possible concentration-efficacy relationship was to be ascertained between plasma concentration of nilvadipine and the observed blood pressure-lowering effect of the drug. Adequate blood pressure reductions were achieved with nilvadipine 8 mg once daily in 13 patients; 7 required a doubling of the dosage to 16 mg/day. Already on the first day of therapy, both the systolic and diastolic blood pressures were significantly reduced compared to those in the placebo phase (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)